The present invention relates to a method for stripping electric cables and a stripping machine to carry out said method. It is well known that proper stripping machines are used to strip the ends of electric cables, carrying out such stripping operation in an automatic or semiautomatic way.
The known stripping machines available on the market are provided with blades with cutting profile put in motion by suitable driving means moving the blades one against the other and the cable arranged therebetween along a rectilinear direction orthogonal to the cable advancement direction.
In order to carry out the stripping operation, the blades are lowered until they incise the sheath of the cable that is then advanced along the longitudinal direction defined by its axes.
In this way the blades that are not yet inserted in the incision made in the sheath, act as resistant element and when the cable is advanced they allow to unthread the sheath cut section.
The above mentioned machines of the prior art have however some drawbacks.
A first drawback consists in that when the cutting profile of the blades is worn, a neat incision of the sheath cannot be obtained and its separation from the cable may result difficult.
This happens especially in the stripping machines carrying out also shearing of the cables by using for the shearing operation the same blades that are used for the stripping operation.
Another drawback consists in that if work is effected with blades having a worn cutting edge, during incision the cable may be squeezed and therefore damaged especially when the cables are of soft material and of small thickness.
The present invention aims at overcoming said drawbacks.
More particularly, a first object of the invention is to provide a method to carry out stripping of electric cables allowing to improve the quality of the sheath incision.
Another object of the method of the invention is to obtain a good incision of the sheath even using blades with imperfectly sharpened cutting edges.
A further object of the method of the invention is to obtain an optimal incision of the sheath even on cables made of soft materials and of small thickness.
A last but not least object of the invention is to provide a machine allowing to carry out the above mentioned stripping method.
The foregoing objects are attained by a stripping method for electric cables that according to the main claim comprises the following steps: arranging the end of at least a cable to be stripped inside a stripping unit; cutting circumferentially the sheath covering said end of said cable for at least a portion of the thickness and at least a portion of the perimeter of said sheath; separating said sheath covering said end from said cable, and wherein said circumferential cut of said sheath is carried out combining at least an action of incision of said sheath with at least an action of rotation of said cable.
According to a first operative mode, the circumferential cut of said sheath comprises sequentially: a first incision of said sheath; a rotation of said cable; a second incision of said sheath, where the action of rotation of said cable starts when the first incision is ended and ends before starting the second incision.
According to a second operative mode, the circumferential cut of said sheath starts before the rotation action and is continued during the rotation action.
According to the invention the above mentioned method is carried out by a stripping machine for electric cables comprising a casing on which there are a stripping unit for said cable; driving means for advancing said cable arranged upstream and downstream said stripping unit; at least a control and actuation microprocessor unit, and wherein said stripping unit comprises at least a cutting unit for incision of the sheath covering at least an end of said cable; at least a rotation unit receiving said cable and putting it in rotation around the longitudinal axis defined by said cable when it is arranged in a rectilinear position.
According to the embodiment that will be described hereinafter, the rotation unit comprises a cable blocking chuck arranged coaxially outside said cable and coupled to driving means putting it in rotation around the longitudinal axis defined by the cable when it is arranged in a rectilinear position.
The blocking chuck comprises in its turn a couple of opposite jaws coupled to driving means adapted to move them mutually one against the other to clamp the cable to be stripped therebetween.
The driving means to put in rotation said rotation unit as well as the driving means to move said jaws, consist of fluidic actuators preferably but not necessarily pneumatic actuators.
Advantageously, use of the method of the invention and of the stripping machine with stripping unit provided with rotary chuck, allow to improve the cutting and stripping quality of cables of any kind.
Still advantageously, the stripping unit with rotary chuck may be applied to stripping machines of any kind and therefore, for instance, to machines that carry out in addition to the cable stripping operation, also the shearing operation of the cable to obtain sections of predetermined length and possibly also stripping of the wires constituting the cable.